Correlations Among Plant Functional Traits In A Temperate Typical Steppe Of Northren China

Plant functional traits,including physiological,morphological,and phenological characteristics,reflect the response and adaptation of plant to the environment change.Plant functional traits link environmental factors,plant individuals,and ecosystem structure and functioning.In recent years,studies on plant functional traits have involved the ecological levels of individual,population,community,and ecosystem,and extended to many ecological research fields.It has been well documented that there are various interrelationships among plant functional traits.The trade-off relationship is one of the most popular correlations among plant functional traits in the previous studies.The trade-off relationship among plant functional traits is also known as the ecological strategy,which is the traits combination making plants occupy the most suitable position on a certain ecological strategy axis after natural selection.Therefore,studies on plant functional traits and their correlations can not only facilitate the understanding of ecosystem processes and functioning,but also reveal the underlying mechanism of species coexistence in a certain region.Grassland,as one of the main biomes all over the world,is an important component of the terrestrial ecosystem.As a part of the Eurasian grassland,the temperate typical grassland in northern China is also an critical traditional animal husbandry base in China.Since the second half of the last century,due to overgrazing,agricultural reclamation and other human activities,as well as climate change,ecosystem degradation and declination in productivity and self-recovery ability have appeared,and consequently impact on the ecological services and the sustainable development strategy of the grassland ecosystem in this region.Therefore,research on plant functional traits and their correlations in the temperate steppe of northern China will facilitate to explain the relationships between plant functional traits and ecosystem functions and provide theoretical support for the formulation of adaptive management strategies and measures to ensure the sustainable development of the regional social and economic development.In this study,twenty-one representative plant communities were selected to investigate and sample plant functional traits during the growing seasons from 2015 to 2017 in the temperate typical steppe of Duolun County,Inner Mongolia.The variation of plant functional traits and their correlations were examined at the species level within community and community level,respectively.The following conclusions were drawn:(1)At the species level,leaf photosynthetic rate was positively correlated with leaf respiration rate and leaf nitrogen content.Leaf mass per area(LMA)increased with leaf life-span(LL)but decreased with leaf respiration rate.The theory of leaf economics spectrum was partly supported by the relationships among leaf traits in the temperate steppe.(2)There were strong correlations between leaf traits and root traits at the species level.Specific root length(SRL)was positively related to the specific leaf area(SLA),whereas negatively correlated with LMA,leaf dry matter content(LDMC),fine root diameter,root depth,and root length.Leaf number per individual,LDMC,and LL increased with root depth and length.It was also found that root diameter was positively correlated with LL but negatively with SLA.(3)An allometric relationships between plant belowground biomass and aboveground biomass was found at species and community levels in the temperate steppe of Inner Mongolia.At the species level,the slope of the relationship between belowground-and aboveground-biomass in the steppe was significant difference than 1,indicating that the investment in the aboveground part of the plant is disproportionately less than that in the belowground part.A similar pattern of biomass allocation was also found for forb.The allometric index of the correlation between belowground-and aboveground-biomass for grass showed no significant difference from 1,suggesting that the growth of belowground and aboveground biomass was isometric.At the community level,the slope of the relationship between the belowground-and aboveground-biomass was significant difference than 1,indicating that the growth rate of the aboveground biomass was less than that of the belowground biomass.However,the growth rates of the belowgroundand aboveground-biomass were isometric in the grazing communities.These findings suggest that there are strong correlations among plant functional traits,as well as the trade-off in resource acquisition,in the temperate typical steppe of in Inner Mongolia.In addition,grazing can alter biomass allocation at the community level,and then may affect ecosystem function and processes in the temperate steppe.